Every 2 weeks currently. Just started adding trace elements to my CA and ALK dose so may start doing monthly soon if the things work out the way I think they will with my triton tests.
I change a between 1-2% each day. As common as AWC is in the hobby you probably should have an option for daily water changes.
Other than my AWC I never manually change water.
i have 2 tanks (180g and 225g ) and change about 5% in each 2x per week. I have a direct line from the RO/Mixing station to 1 tank which makes water changes very easy. The smaller one i have to do using buckets and a pump ... but it's kind of a meditation and it feels good to give the tanks some extra love